Studio degli NOx: formazione ed evoluzione in atmosfera = A study on NOx: formation and evolution in the atmosphere

A thorough knowledge of the behaviour of certain chemical compounds responsible for atmospheric pollution, and a correct evaluation of the state of air quality, represent the key points on which to base specific interventions that aim to reduce and/or eliminate possible repercussions on the ecosystem and on human health. This thesis work, based on the historical studies carried out on the formation and reaction of NOx in the atmosphere and on the empirical reports produced in previous studies, analysed the historical series of NOx, NO2, NO and O3 concentrations detected in the period 2015 - 2019 by two monitoring stations of the Regional Air Quality Monitoring System of the Piedmont Region, both located in the city of Turin. The study examined the distribution of NOx and NO2 concentrations in different time bands, highlighting some differences in the dispersion of the validated data and eventually obtaining specific empirical relationships for the determination of NO2 concentration values as a function of the NOx ones. Dissonances were recorded not only in the analysis of the different time bands but also between the concentration distributions of the two monitoring stations. In particular, higher values of the NO2/NOx ratio have been observed in the measurements of the Lingotto station, suggesting a reflection on the link between a greater contribution of emissions in the atmosphere and the industrial/residential urban context that characterises the station’s surroundings. At the same time, the interrelationships between nitrogenous species and tropospheric ozone were also investigated, outlining in the first analysis the trend of concentrations in the period under examination (2015-2019), and then observing the evolution of concentration averages over 24 hours. Finally, with reference to the data for 2018, based on the evidence found in the analysis of the scatter plots for to the hot and cold seasons, an in-depth study has been conducted on the incidence of temperature variation on nitrogen oxide concentrations, which has observed an increase in NO2 concentrations as the temperature decreases.